Surface integrated waveguide including top and bottom conductive layers having at least one slot with a specific contour

Abstract

A waveguide for electromagnetic radiation, which is a substrate integrated waveguide which is basically a laminate of planar layers includes a substrate layer of dielectric material; a bottom layer and a top layer of an electrically conductive material provided on the respective bottom surface and top surface of the substrate layer; a multitude of pillars of electrically conductive material which extend through the substrate layer from its bottom to its top surface and which are electrically connected to the bottom and top layer; wherein at least one of the bottom and top layer contains at least one part that is void of electrically conductive material, which part is referred to as a slot.

Claims

1. A waveguide for electromagnetic radiation, which is a substrate integrated waveguide, comprising: a substrate layer of dielectric material; a bottom layer and a top layer each formed from an electrically conductive material provided on a respective bottom surface and top surface of the substrate layer; a plurality of pillars of electrically conductive material which extend through the substrate layer from the bottom surface to the top surface and which are electrically connected to the bottom layer and top layer; wherein at least one of the bottom layer and top layer contains at least one part that is void of said electrically conductive material, said at least one part is referred to as a slot; wherein the at least one slot is delimited, in the plane of the respective layer in which the at least one slot is present, by a contour which is defined by an x and y coordinate which fulfils the following equations:
x(ϕ)=c.sub.xR(ϕ)cos(ϕ)
y(ϕ)=c.sub.yR(ϕ)sin(ϕ) wherein: $R\left(\varphi \right)={\left[{.Math.\frac{\cos \left(\frac{m_1\varphi }{4}\right)}{a_1}.Math.}^{n_1}+{.Math.\frac{\sin \left(\frac{m_2\varphi }{4}\right)}{a_2}.Math.}^{n_2}\right]}^{\frac{1}{b_1}}$ wherein the values for the parameters c.sub.x, c.sub.y, m.sub.1, m.sub.2, a.sub.1, a.sub.2, n.sub.1, n.sub.2 and b.sub.1 are selected from a group of real numbers of positive value, and ϕ is an angular coordinate that covers a range from −π to π; wherein the contour is not of a rectangular shape, not of a rounded rectangular shape, and not of a cross-shape.

2. The waveguide according to claim 1, wherein at least one of the bottom layer and top layer contains a multitude of slots which include the at least one slot, wherein each individual slot is respectively delimited by the contour, such that the multitude of slots form a number of linear arrays of slots, wherein the number of linear arrays of slots are disposed adjacent to each other and in a parallel direction to each other, so that a grid of slots is formed, wherein the slots per linear array are disposed on a line extending parallel to a longitudinal direction of the waveguide, wherein the slots per linear array are spaced apart from each other by a distance in the longitudinal direction of the waveguide, wherein the plurality of pillars includes at least one row of pillars, and a row of pillars is provided between adjacent linear arrays of slots, wherein the substrate layer includes a plurality of circumferential sides and the row of pillars is disposed proximal to the circumferential sides of the substrate layer, wherein one circumferential side of the substrate layer is not provided with the row of pillars.

3. The waveguide according to claim 2, wherein the number of linear arrays of slots is 3 to 5.

4. The waveguide according to claim 1, wherein the contour of the at least one slot has a shape similar to a two-dimensional contour of either a hat or a bow-tie, and said shape is oriented in a longitudinal direction of the waveguide.

5. The waveguide according to claim 1, wherein the contour is defined by the following parameters: c.sub.x is chosen from the range 6.0×10.sup.−5 to 8.0×10.sup.−5, c.sub.y is chosen from the range 7.4×10.sup.−4 to 9.6×10.sup.−4, m.sub.1=2.8, m.sub.2=3.2, a.sub.1=a.sub.2=1, n.sub.1=n.sub.2=5 and b.sub.1=2.

6. The waveguide according to claim 1, wherein the contour is defined by the following parameters: c.sub.x is chosen from the range 4.0×10.sup.−6 to 9.0×10.sup.−5, c.sub.y is chosen from the range 1.25×10.sup.−6 to 3.8×10.sup.−5, m.sub.1=4, m.sub.2=0.5, a.sub.1=a.sub.22=1, n.sub.1=5, n.sub.2=8, and b.sub.1 is chosen from the range of 2 up to 4.

7. The waveguide according to claim 1, wherein at least one of the bottom layer and top layer contains a multitude of slots which include the at least one slot, wherein each individual slot respectively is delimited by the contour, such that the multitude of slots form at least one linear array of slots, wherein said linear array of slots is disposed on a line extending in a longitudinal direction of the waveguide, and wherein adjacent slots of the said linear array of slots are spaced apart from each other by a distance in the longitudinal direction of the waveguide.

8. The waveguide according to claim 7, wherein respective central points of the individual slots of the at least one linear array of slots are positioned at a pre-determined offset distance from the longitudinal axis of the waveguide, and wherein respective central points of adjacent slots of the said linear array of slots are positioned on different sides of the longitudinal axis projected on the respective layer.

9. The waveguide according to claim 7, wherein the distance between respective central points of adjacent slots in the longitudinal direction of the waveguide is half of the guided wavelength of a signal that is applied to the waveguide.

10. The waveguide according to claim 7, wherein the number of slots contained in the at least one linear array of slots is 6 to 10.

11. The waveguide according to claim 7, which has a length that corresponds to a guided wavelength of a signal that is applied to the waveguide, and which is multiplied by a factor of 3 to 5.

12. The waveguide according to claim 1, wherein the contour of the at least one slot has a slot length which lies in the range of 1.8 to 2.7 mm.

13. The waveguide according to claim 1, wherein the contour of the at least one slot has a slot width which lies in the range of 0.24 to 0.32 mm.

14. The waveguide according to claim 1, wherein the substrate layer, the bottom layer and the top layer each have a rectangular circumference in a plane of the respective layer.

15. The waveguide according to claim 1, wherein the waveguide is effective for electromagnetic radiation in the frequency range from 58 to 62 GHz.

16. The waveguide according to claim 1, wherein the at least one the slot has a respective central point that is positioned at an offset distance (Δ) from a longitudinal axis of the waveguide which lies in the range of 0.20 to 0.30 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be further elucidated herein below with reference to the attached drawings of which:

(2) FIG. 1 shows a top view of a single slot waveguide according to a preferred primary embodiment of the invention;

(3) FIG. 1a shows a longitudinal cross-section of the waveguide of FIG. 1;

(4) FIG. 2 shows a top view of a waveguide according to a preferred secondary embodiment of the invention;

(5) FIG. 3 shows a top view of a waveguide according to a preferred tertiary embodiment of the invention;

(6) FIG. 4a shows a first group of single slot waveguides with a preferred contour of the slot;

(7) FIG. 4b shows a first group of single slot waveguides with a preferred contour of the slot;

(8) FIG. 4c shows a first group of single slot waveguides with a preferred contour of the slot;

(9) FIG. 5a shows a second group of single slot waveguides with a preferred contour of the slot;

(10) FIG. 5b shows a second group of single slot waveguides with a preferred contour of the slot;

(11) FIG. 5c shows a second group of single slot waveguides with a preferred contour of the slot;

(12) FIG. 6 shows test results for the first group of single slot waveguides;

(13) FIG. 7 shows a test result for a waveguide based on a linear array of the slot;

(14) FIG. 8a shows a test result for a waveguide based on a linear array of the slot;

(15) FIG. 8b shows a test result for a waveguide based on a linear array of the slot;

(16) FIG. 8c shows a test result for a waveguide based on a linear array of the slot;

(17) FIG. 9 shows test results for a waveguide based on a grid of slots.

DETAILED DESCRIPTION OF THE INVENTION

(18) FIG. 1 shows a top view of a single slot waveguide 1 having a longitudinal axis 1.sub.a, which is provided with a top layer 7 of a rectangular form. The top layer is provided on a non-visible substrate layer 5 which has the same form and size as the top layer 7. The opposed bottom surface of the substrate layer 5 is covered with a bottom layer 9 (FIG. 1A).

(19) The circles indicate a row of non-visible pillars 11 that are connected to the bottom side of the top layer 7 and extend through the underlying substrate layer 5 as further indicated in FIG. 1a and are connected to the bottom layer 9. The pillars 11 have a diameter d, and a regular distance A between the centers of consecutive pillars in a row. The pillars are provided in a row of separate pillars that are disposed proximal to the circumferential sides of the substrate layer 5. At one circumferential side 20, the substrate layer 5 is not provided with a row of pillars 11. This side 20 functions as an entry side or port side for electromagnetic radiation.

(20) The pillars 11, the bottom layer 9 and the top layer 7 are made from copper. The substrate layer 5 is made from a dielectric material.

(21) When electromagnetic radiation of 60 GHz is applied to the single slot waveguide according to FIG. 1, the guided wavelength λ.sub.g is approximately 4.64 mm.

(22) The length of the waveguide is about ¾ of the guided wavelength λ.sub.g for which the waveguide is suited, for instance about 3.50 mm.

(23) The overall width of the waveguide is related to the optimum width W.sub.SI between directly opposed pillars at two longitudinal sides of the waveguide. The width W.sub.SI corresponds to about 2.8 mm, which value may vary by 0.2 mm. The resulting overall width of the waveguide is about 3.6 mm.

(24) The diameter of the pillars is about 0.4 mm and the distance A between the pillars is about 0.6 mm.

(25) The top layer 7 is provided with a slot 12 having a contour 14 of a butterfly shape. The slot is a removed part of the layer 7, thus revealing a part of the underlying substrate layer 5. The butterfly shape is a contour that fulfils the equations for the x coordinate and y coordinate according to the present invention.

(26) The contour 14 of the slot 12 has a maximum width W.sub.slot and a maximum length Loot.

(27) The slot 12 has a central point 16 which lies at the crossing of the mean value of the slot width indicated by the line mW and the mean value of the slot length indicated by the line mL.

(28) The central point of the slot 16 is located half a guided wavelength λ.sub.g/2 from the entry side 20, measured in the longitudinal direction.

(29) The central point of the slot 16 is located about ¼ of the guided wavelength λ.sub.g/4 from the most proximal pillars, measured in the longitudinal direction.

(30) The central point of the slot 16 is present in transverse direction at a pre-selected offset distance A from the longitudinal axis 1.sub.a projected on the respective layer 7. FIG. 1A shows a longitudinal cross-section of the waveguide 1 of FIG. 1, along the longitudinal axis 1.sub.a. Onto the substrate layer 5 are provided a top layer 7 and a bottom layer 9, which are made from copper. The substrate layer 5 has a relative permittivity εr of 2.2, and is made of RT/DUROID® 5880 material. The thickness of the substrate layer is 0.50 mm. The exact thickness of the copper layers is less critical, and are merely shown schematically. The non-visible pillars 11 located at circumferential sides of the substrate layer 5, are indicated by dotted lines and establish the connection between the top and bottom layers 7 and 9.

(31) FIG. 2 shows a top view of a waveguide 40 having a longitudinal axis 1.sub.a, which is provided with a top layer 7 of a rectangular form. The top layer is provided on a non-visible substrate layer 5 (FIG. 1) which has the same form and size as the top layer 7. The opposed bottom surface of the substrate layer is covered with a bottom layer 9 (FIG. 1A).

(32) Analogously to FIG. 1, the circles indicate a row of non-visible pillars 11 that are connected to the bottom side of the top layer and extend through the underlying substrate layer and are connected on the other side of the substrate layer to a bottom layer.

(33) The top layer 7 is provided with a linear array of slots 12, each slot having a contour of a butterfly shape. The slots 12 in the array are disposed on a line extending in the longitudinal direction of the waveguide, wherein the slots are spaced apart from each other by a regular distance in the longitudinal direction, which distance is about half the value of the guided wavelength (i.e., λ.sub.g/2). The distance is measured between the central points 16 of adjacent slots. The zig-zag line l.sub.z, indicates an interruption of the depicted linear array, which actually contains eight slots, and not just three as indicated in FIG. 2. An image of such a full configuration with eight slots is shown in another attached figure.

(34) With regard to the positioning of the slots 12, it is remarked that the central points of the slots are positioned at a pre-determined offset distance A, and that the central points of adjacent slots are positioned on different sides of the central longitudinal axis 1.sub.a projected on the respective layer.

(35) Further indicated values and reference numbers have an equal meaning as the ones given in respect of FIG. 1 for the single slot waveguide, with the exception of the offset value which is 0.10 mm, instead of 0.25 mm in FIG. 1.

(36) FIG. 3 shows a top view of a waveguide 60 having a longitudinal axis 1.sub.a, which is provided with a top layer 7 of a rectangular form. The top layer is provided on a non-visible substrate layer 5 (FIG. 1) which has the same form and size as the top layer 7. The opposed bottom surface of the substrate layer is covered with a bottom layer 9 (FIG. 1).

(37) Analogously to FIG. 2, the circles indicate rows of non-visible pillars 11 that are connected to the bottom side of the top layer and extend through the underlying substrate layer and are connected on the other side of the substrate layer to a bottom layer.

(38) The top layer is provided with four linear arrays of slots 12H, 12B, which are disposed adjacent to each other and in parallel direction to the longitudinal axis 1.sub.a, so that a grid of slots is formed. In each linear array, the slots 12H, 12B, are spaced apart from each other in the same manner as indicated in FIG. 2, by a half of the guided wavelength. Analogously, the offset distance alternates per adjacent slot in a linear array of slots. One linear array has slots that have a contour of a so-called “bow-tie shape” 12B, the other linear arrays have slots with a contour of a so-called “hat shape” 12H. Both these shapes will be further explained below.

(39) Between adjacent linear arrays a row of separate pillars 11 is provided. Furthermore, a row of separate pillars is disposed proximal to the circumferential sides of the substrate layer. Each linear array has a respective entry side 20 which is devoid of pillars 11.

(40) FIGS. 4a), 4b) and 4c) respectively show a top view of a first group of single slot waveguides with a preferred contour of the slot of which the x coordinate and y coordinate of the above equations are based on the indicated choice of parameters and applied in the equations according to the invention.

(41) In FIG. 4a, (Gielis #9), m.sub.1=2.8, m.sub.2=3.2, a.sub.1=a.sub.2=1, n.sub.1=n.sub.2=5, b.sub.1=2, Δ=0.25 mm, c.sub.x=8.1×10.sup.−5, and c.sub.y=9.6×10.sup.−4. In FIG. 4b, (Gielis #15), m.sub.1=2.8, m.sub.2=3.2, a.sub.1=a.sub.2=1, n.sub.1=10, n.sub.2=5, b.sub.1=2, Δ=0.25 mm, c.sub.x=6×10.sup.−5, and c.sub.y=7.38×10.sup.−4. In FIG. 4c, (Gielis #16), m.sub.1=2.8, m.sub.2=3.2, a.sub.1=1, n.sub.1=5, n.sub.2=8, b.sub.1=2, Δ=0.25 mm, c.sub.x=6.38×10.sup.−5, and c.sub.y=8.2×10.sup.−4.

(42) The three waveguides include the same basic properties already shown in FIG. 1, only the contour of the slot is different. The slots of these waveguides have a general contour in common, that is hereby indicated as a ‘hat shape’. Further, the shown waveguides are single slot waveguides that include a top layer 7, pillars 11, and a slot 12.

(43) The hat shape in FIGS. 4a) to 4c) is based on a circumference comprising a line X1 (FIG. 4a) that runs straight and parallel to the longitudinal direction of the waveguide, and an opposed line X2 (FIG. 4a) of which the middle part is at a further distance from the straight side than the complementing parts adjacent to the middle part, so that the slot has an enlarged width over the middle part of its slot length in comparison to complementing parts adjacent to the middle part.

(44) FIGS. 5a), 5b) and 5c) respectively show shows a second group of single slot waveguides with a preferred contour of the slot of which the x coordinate and y coordinate of the above equations are based on the indicated choice of parameters and applied in the equations according to the invention. In FIG. 5a, (Gielis #12), m.sub.1=1, m.sub.2=0.5, a.sub.1=a.sub.2=1, n.sub.1=5, n.sub.2=8, b.sub.1=2, Δ=0.25 mm, c.sub.x=4.15×10.sup.−6, and c.sub.y=9.6×10.sup.−6. In FIG. 5b, (Gielis #13), m.sub.1=4, m.sub.2=0.5, a.sub.1=a.sub.2=1, n.sub.1=5, n.sub.2=8, b.sub.1=3, Δ=0.25 mm, c.sub.x=3.29×10.sup.−5, and c.sub.y=1.18×10.sup.−5. In FIG. 5c, (Gielis #14), m.sub.1=4, m.sub.2=0.5, a.sub.1=1, n.sub.1=5, n.sub.2=8, b.sub.1=4, Δ=0.25 mm, c.sub.x=8.85×10.sup.−5, and c.sub.y=3.8×10.sup.−4.

(45) The three waveguides include the same basic properties already shown in FIG. 1, only the contour of the slot is different. The slots of these waveguides have a general contour in common, that is hereby indicated as a ‘bow-tie shape’. Further, the shown waveguides are single slot waveguides that include a top layer 7, pillars 11, and a slot 12

(46) The bow-tie shape is based on a circumference of two lobes connected at a narrowed central section wherein the shape is oriented in the longitudinal direction of the waveguide.

(47) FIG. 6 shows a graph of the measured peak realized gain in dB over the frequency range 58-62 GHz, when using the first group of single slot waveguides, which are coded as G9, G15, and G16 in accordance with the numbering in FIG. 4. The letter G indicates a contour compliant with the Gielis formula according to the invention. For comparison, a graph for a single slot waveguide from the prior art having a rectangular slot (which is indicated as R) is included as well. It can be appreciated, with respect to FIGS. 6, 7, 8a, 8b and 8c, that the horizontal axis corresponds to the frequency range and the vertical axis corresponds to the peak gain.

(48) The graph clearly shows that all three variants of the first group of single slot waveguides according to the invention achieve a significantly enhanced peak gain value. Furthermore, this enhancement is achieved over the whole frequency range, and without substantial drops in peak gain of a magnitude observed for the prior art waveguide.

(49) FIGS. 7 and 8a, 8b, and 8c show graphs of the measured peak realized gain in dB over the frequency range 58-62 GHz, when using several types of waveguides based on a linear array of slots, i.e. the secondary embodiment of the invention. All waveguides were based on an array of 8 slots, and were disposed on the top layer as shown in FIG. 2.

(50) In FIG. 7, the results for three waveguides LG9, LG15 and LG16, are depicted in comparison to a prior art waveguide based on a linear array of rectangular slots (LR). Each waveguide according to the invention was provided with slots of a specific shape that corresponds to the numbering 9, 15, and 16, that is used and depicted in FIG. 4. The letter L indicates the waveguide structure is integrated with a linear array of slots.

(51) In FIGS. 8a, 8b, and 8c, respectively, the results for three waveguides LG12, LG13 and LG14, are depicted. Each of these waveguides was provided with slots of a specific shape that corresponds to the numbering 12, 13, and 14, that is used and depicted in FIG. 5.

(52) In terms of results, FIG. 7 shows that LG9 and LG15 achieve a significantly enhanced peak gain value in dB. Furthermore, this enhancement is achieved over the whole frequency range, and without substantial drops in peak gain of a magnitude observed for the prior art waveguide. LG16 achieves a significantly enhanced peak gain value in the range 61-62 GHz, and has a peak gain comparable to LR in the range 58-61 GHz. LG16 has no substantial drops in peak gain of a magnitude observed for the prior art waveguide.

(53) In terms of results, LG12 (FIG. 8a), LG13 (FIG. 8b) and LG14 (FIG. 8c), respectively, achieve a significantly enhanced peak gain value over LR (FIG. 7). Furthermore, this enhancement is achieved over the whole frequency range.

(54) FIG. 9 shows a graph of the measured peak realized gain over the frequency range 58-62 GHz, when using a waveguide based on a grid of slots, i.e. the tertiary embodiment of the invention.

(55) This waveguide is based on 4 parallel disposed linear arrays, each array containing 8 slots, and disposed on the top layer in the manner shown in FIG. 3. Different from the configuration shown in FIG. 3, all slots have the same shape which corresponds to the one shown in FIG. 4a), which has the number code 9. Accordingly, the waveguide is coded GG9, wherein the first letter G indicates that the waveguide is integrated with a grid of slots according to the tertiary embodiment.

(56) A comparison was made by performing the same measurements for an analogously configured grid of slots that in contrast was based on prior art rectangular slots. The graph for this prior art grid of slots is indicated as GR.

(57) In terms of results, the tertiary embodiment of the waveguide which is exemplified by GG9, achieves an enhanced peak gain value in the ranges of 58-60 GHz and 61.2-62 GHz. Furthermore, GG9 has no substantial drops in peak gain of a magnitude observed for the prior art waveguide, this is most notable in the range of 61.2-62 GHz.